Base plate of grenade mortar



Oct. 9, 1956 H. o. DONNER BASE PLATE OF GRENADE MORTAR Filed May 12, 1953 INVENTORQ I Hans 0t 30 fimm er 8Y9 rg BASE PLATE F GRENADE MORTAR Hans Otto Donner, Tampere, Finland, assignor to Soltam Ltd., Haifa, Israel Application May 12, 1953, Serial No. 354,607

6 Claims. (Cl. 8937) This invention relates to a base plate structure of grenade mortars. The mortar base plate, as is well known, is a plate-like piece having a central cup in which the breech end base cap of the mortar rests. The under side of the base plate engages the ground and it is the object of the base plate to provide a rigid structure which will firmly stay in place when the mortar is fired. Hence, the base plate transmits the recoil forces directly to the ground.

Because the ground in many cases is very soft the surface area of the base plate must be appreciable. Then too, because the breech end base cap rests in a cup provided therefor in the base plate and the recoil forces 0ccasioned by firing are transmitted from the said cup through the base plate to a greater surface area extent of the ground the base plate must be of very rigid structure.

Prior known base plate structures are generally platelike and ordinarily made of high quality steel sheeting reinforced with rolled grooves and welded ribs to with stand appreciable bending stresses. Ordinarily the base plate is shaped to form a square or parallelogram. To impart sufficiently great rigidity to the plate-like structure it is necessary, firstly, that the plate be made comparatively thick and, secondly, that the reinforcing ribs be exceedingly strong and that a multiplicity of these ribs be arranged in the plate. For these reasons the base plate is exceedingly heavy in weight. By way of example mention is here made of the fact that a base plate for an 81 mm. mortar will weigh about 22 kilograms.

This invention has for its object to provide a light weight base plate of rigid construction which will stand firmly in place when the mortar is fired in any direction whatever, and it is another object of the invention to provide a base plate which can be used in exceedingly low elevation angle firing.

The novelty of the invention lies in that the cup for the breech end base cap is disposed centrally within the top part of a downwardly opening cone of metal while a second upwardly opening conical surface extends upwardly from the lower part of said first mentioned cone, partly to lie thereupon but in the main on the exterior side thereof, said two conical surfaces then being reinforced with angle irons and ribs. 7

These and other objects and advantages will be apparent as the specification is considered with the accompanying drawing wherein a base plate embodying the invention is shown by way of example only. It is to be understood that the invention is not limited to the embodiment shown nor otherwise than by the terms of the appended claims.

In the accompanying drawing:-

Fig. l is a side elevational view of a grenade mortar base plate, partially in section; and

Fig. 2 is a top plan view of the same, one fourth in section along line IIII of Fig. 1.

The base plate, according to the present invention, has its center a cup 1 for receiving the breech end base cap of a mortar. To the upper edge of the cup 1 is welded 2,765,707 Patented 0a. s, 1956 a downwardly opening conical plate 2. To the lower edge of the conical plate 2 is, in its turn, welded an inverted or upwardly opening conical plate 3 and a disc 4 extends between the upper edge of the cup 1 and the upper edge of the conical plate 3. From the junction line of the cone 3 and the disc 4 there extends outwardly an upwardly opening inverted conical plate 5, the outer edge of which is strengthened by a conical annular ring 6. The cones 6, 5 and 3 are further reinforced with V-shaped irons 7 and the plate disc 4 and the cones 3 and 2 are reinforced with internal strengthening plates 8. Down to its very bottom part the cup 1 is, moreover, connected for support to the cone 2 by interplates 9. For carrying the base plate the same is provided with a suitable handle 10 and, moreover, with various kinds of locking means 11, e. g., for attachment to a firing means or vehicles. Moreover, the upper edge of the cup 1 is provided with a guard 12 for preventing sand from running into the cup 1 and depending upon the structure of the breech end base cap with a locking plate or locking means 13 adapted to prevent the cap from rising out of the cup 1 during firing.

Let us now study the stresses and tensions occasioned by firing on the base plate made according to the teachings of this invention. First, if a downward and sideward directed force acts upon the cup 1, in the main a downward pressing stress occurs in the plane of the cone 2. When the lower edge and under side of the said plate engage the ground, tensile stress occurs in the plate in the bottom part of the cone as the cone tends to open up. Hence we note that the invention most advantageously utilizes structure material in that the acting forces are changed into downward pressing stress and tensile stress thereby preventing the bending of the base plate proper. Similar advantageous distribution of forces applies to the cones 3 and 5. In consequence of this it is possible to reduce the weight of the base plate of an 81 mm. mortar from 22 to 12 kilograms. Further, the round and symmetrical structure of the base plate provides same firing possibilities in all directions. And furthermore, because the ball and cup joint is located exceedingly low, during firing, the edge of the base plate will never tend to rise from the ground, but the base plate will stand firmly in place even in firing with low elevation angles. Because it is customary to fire chiefly in one direction only the base plate can be made eccentric, e. g., so that the uppermost cone is longer and higher on the one side thereof, in which case the cup 1 will be located eccentrically relative the periphery of the base plate. Then during firing, the rear side of the base plate will carry more than the fore side.

Having described my invention, what I claim as new and desire to secure by U. S. Letters Patent is:

1. A base plate for a grenade mortar, comprising an upwardly opening cup for receiving the breech end base cap of a mortar, a downwardly opening first frusto conical plate having said cup mounted centrally in the top thereof, an upwardly opening second frusto conical plate joined to said first frusto conical plate at the bottom thereof and extended upward and outward therefrom, and an annular connecting plate extending between the upper edges of said first and second frusto-conical plates.

2. A base plate according to claim 1, including a third frusto-conical plate opening upwardly and extended upward and outward from the upper edge of said second frusto conical plate, and an outwardly and downwardly flared ring reinforcing the top periphery of said third frusto conical plate.

3. A base plate according to claim 2, wherein said first frusto conical plate and said second frusto conical plate are secured to each other and to said cup by radially extended internal strengthening plates.

References Cited in the file of this patent UNITED STATES PATENTS Gerhardt June 26, 1951 Weiss et al June 26, 1951 FOREIGN PATENTS France June 24, 1935 Great Britain Oct. 25, 1938 Switzerland Sept. 17, 1951 

